Wireless systems typically include a receiver synchronizing to a desired signal, and receiving information from the desired signal. In some situations, the transmitter of the desired signal is proximate to other transmitters that transmit signals that interfere with the desired signal, and can be considered as noise and/or interference.
Interference can impair a receiver's ability to properly detect the start of a packet of information of the desired signal. Specifically, the receiver can synchronize to an interfering signal or noise (referred to as a “false” synchronization) which can result in missed detection of the desired signal. This is particularly probable when the interfering signals and the desired signals are transmitted overlapping in time. Additionally, the interference can degrade the synchronization properties of the desired signal, thereby inhibiting the receiver from detecting the desired signal.
In many wireless systems, the interference signals from adjacent channels or even nearby (in frequency) can impair the receiver's ability to synchronize to the desired signal. A proposed solution includes attempting to filter out of band interference using low pass filters. Therefore, when the receiver samples the signal at the desired sampling rate, the aliasing component of the interference signals can be reduced. However, there are practical limitations on the ability of the receiver low pass filters to reject the out of band interference. First the interference is typically not adequately suppressed, or the low pass filtering degrades the overall decoding of the desired signal by introducing extensive inter-symbol interference which degrades the signal quality of the desired signal.
It is desirable to have methods and apparatuses for enhancing synchronization to a desired signal.